Melatonin is a hormone synthesized in the pineal gland and the retina. The molecule is a lipophilic indole which has been difficult to localize cytochemically. We have used a polyconal sheep antiserum (CIDtech Res.Inc., Hamilton, Canada) to visualize the localization of melatonin in the pineal complex of the Golden hamster and the rat. The animals were perfused through the vascular system with at solution of 4% paraformaldehyde in 0.1 M phosphate buffer. After cryoprotection in 20% sucrose, 20 µm thick cryostat sections were cut and reacted for melatonin by using the PAP technique. Staining for melatonin was observed both in the superficial pineal gland and in the deep pineal gland as well as in the pineal stalk of both the hamster and rat. The staining was abolished after incubation of the specific antiserum with melatonin. Staining was observed in the majority of pineal cells but never in perivascular spaces. In the cells, the staining was confined to the cytoplasm but never to the nuclei. Melatonin staining was also observed in cellular processes located in the luminal part of the ependyma covering the pineal recess. Thus, our study shows that all parts of the pineal complex in rodents synthesize melatonin. Our study does not support a nuclear localization of melatonin. Finally, melatonin might be secreted to the ventricular fluid via cellular processes reaching the ependyma of the third ventricle.

Back to the top.Presentation Number SAmøller0874Keywords:melatonin, rat, hamster, cytochemistry